Mounting guard rings are known, for example, from DE 38 38 760. In essence, a mounting guard ring consist of a plastic protective ring which, on its outer periphery, has a supporting surface for the sealing lip of a sealing ring. The sealing ring is pushed onto the supporting surface.
Mounting guard rings are used for the storage and transportation of sealing rings, particularly sealing rings with PTFE sealing lips, because without being subjected to pressure such rings have a tendency to undergo elastic recovery as a result of a memory effect.
Moreover, mounting guard rings are used in the mounting of sealing rings onto a shaft. During the mounting of the sealing ring onto a shaft, the protective ring of the mounting guard ring protects the sealing lip of the sealing ring from damage by sharp-edged transition regions or sharp-edged profiles as, for example, multi-tooth or grooved wedge profiles. When passing over sharp-edged transition regions or profiles, the sealing lips of sealing rings can be damaged which would cause immediate leakage or a reduction in service life of the sealing ring. After the mounting of the sealing ring, the mounting guard ring is manually removed axially from the shaft.
Units consisting of a sealing ring and a mounting guard ring are often pre-mounted in a housing. Prior-art mounting guard rings, however, have the drawback that dirt or paint dust can penetrate into the housing through the opening of the mounting guard ring so that the housing becomes filled with a lubricant or preservative agent that cannot be transported.